Highway 140, which is a main road into Yosemite National Park, remains open.

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MARIPOSA, Calif. (AP) An unattended campfire near a main route into Yosemite National Park has grown into a more than 2-square-mile blaze that officials said Tuesday has led to the evacuations of 800 homes and 1,500 people.

California Department of Forestry and Fire Protection officials released the cause of the fire Tuesday, as 2,200 firefighters - up from more than 700 on Monday - worked to gain the upper hand on it amid windy, dry conditions.

No other details were available about where the fire started Sunday, spokeswoman Karen Guillemin said.

The fire 6 miles northeast of Mariposa remains 15 percent contained. Though temperatures were down, officials feared the weather conditions could still fuel the flames, officials said.

The fire has not grown in size from Monday evening, but is burning on the interior, Guillemin said.

One firefighter suffered a minor injury in the fire, but no structures have been damaged or destroyed. Crews are clearing brush to create defensive space around homes, laying fire line and dropping retardant from the air.

Firefighters in Colorado were mopping up remaining hot spots from the most destructive wildfire in state history. The Black Forest Fire just outside Colorado Springs killed two, destroyed 502 homes and charred more than 22 square miles. It was 85 percent contained Tuesday as hundreds of evacuated residents were allowed back into the burn area, though they were warned that many would return to rubble, not their homes. Colorado firefighters were also finishing work putting out a wildfire that burned 5 square miles near Canon City in southern Colorado.

A wind-whipped 20-acre wildfire in northern Arizona on Tuesday has forced the evacuations of some homeowners west of Prescott in Yavapai County. The fire triggered mandatory evacuations for homeowners in the Granite Basin area and people in the Alto Pit Recreation Area. It isn't immediately clear how many people have been evacuated and authorities didn't know how the fire started. Wildfires have also charred nearly 100 square miles of dry, rugged terrain across New Mexico since the end of May, with the largest fire still raging in the Gila National Forest.

Hot, windy weather helped the 39-square-mile Silver Fire grow overnight and firefighters were concerned since critical fire weather was expected through the rest of the week. No homes have burned in New Mexico, but land managers in the Gila and Santa Fe National Forests were already bracing Tuesday for the post-fire threats of erosion and flooding from summer rains.

In Mariposa, Highway 140 into Yosemite National Park remains open.

Tourists can see some smoke from the road itself, but it does not affect visitors in the park, said Yosemite National Park spokesman Scott Gediman. The fire is burning about 35 miles west of the park boundary, Gediman said.

"Visitors coming into the park are fine,'' he said. "We're not discouraging visits, just the opposite. If people have plans, there's absolutely no reason for them not to come.''

Fire officials said fire danger is extreme in California this year, due to an especially dry spring. Already this year, more than 51,000 acres have burned across the state. At this time last year, only 19,000 acres had burned.

Cal Fire has responded to 2,600 fires so far in 2013, a 75% increase from 2012, officials said.

Samantha Weber, who lives in Midpines, a rugged, unincorporated area about 35 miles west of Yosemite, said she knew the fire near Yosemite was headed for her home when she saw charred leaves drifting at her.

"I saw entire leaves that are blackened and blistered just floating through the air,'' Weber told the San Francisco Chronicle. "They looked like birds.''

The fire was helped by swirling winds and dry conditions that residents said are severe and arrived surprisingly early this year.

"It is kind of always dry here in the summer,'' Weber said. "But it was an especially dry spring, so things are really dry.''

Ed Helms, his wife and three adult children were told to evacuate their home in Hites Cove on Sunday as they celebrated Father's Day in the backyard.

"We had to leave the steaks we were cooking on the barbecue to pack up and get out,'' Helms told the Modesto Bee.

The Red Cross has set up a shelter in Mariposa for evacuees. An estimated 94 percent of wildfires have human causes, Guillemin said.

"Humans need to stop and think fire prevention before they do anything outdoors, so they can help prevent fires,'' she said.